Superior lead-free high-temperature piezoceramics of BiFeO3–BaTiO3–(Bi0.5Na0.5)TiO3 through cooperative regulation

Abstract

How to overcome the contradiction between the piezoelectric coefficient (d₃₃) and Curie temperature (T_c) is a long-term challenge for practical applications of high-temperature piezoelectric ceramics. Here, we introduce a strategy to simultaneously enhance d₃₃ and T_c values in 0.69Bi_1.02Fe_(1−x)(Mg_2/3Nb_1/3)_xO₃-0.29BaTiO₃-0.02(Bi_0.5Na_0.5)TiO₃ (BF(MN)_x–BT–BNT) compositions close to the rhombohedral-pseudocubic morphotropic phase boundary by cooperatively regulating the lattice distortion and content of the rhombohedral phase, domain heterogeneity and defect concentration. The d₃₃ and T_c values increase from ∼180 pC N⁻¹ and ∼460 °C to ∼240 pC N⁻¹ and ∼482 °C with increasing (Mg_2/3Nb_1/3)³⁺ content from x = 0 to x = 0.003. The synergistic effect of the increased lattice distortion, decreased rhombohedral phase content, enhanced domain heterogeneity and reduced defect concentration is responsible for the significantly enhanced piezoelectricity, while the competition effect between the increase of the lattice distortion and the decrease of the rhombohedral phase content leads to an improved T_c. These results provide a new strategy for compositionally designing ideal high-temperature piezoelectric ceramics in BF–BT based and other perovskite-structured piezoelectric ceramics.